Currently optical fiber illumination elements such as element 12 shown in FIG. 1 are used exclusively in medical illumination where small packaging is critical. Devices such as endoscope 10 are the most common devices that currently use optical fiber illumination. Due to its compact size, optical fiber is an excellent choice for rigid endoscope illumination. However, there are complications using optical fiber illumination in flexible endoscope applications.
Although the cost of raw glass or plastic fiber is relatively inexpensive, the cost of assembling the fiber into an endoscope tube may be high. Once the fiber is inserted, it generally must be glued and polished to a specific angle.
Optical fiber is extremely fragile and brittle. During the assembly process or in the field after many sterilization cycles, optical fiber may start to break down and degrade. Color change is also very common with fiber optics after many sterilization cycles. Since the fiber is integrated into endoscopes, any damage to the fiber optics also results in damage to the scope, thus causing an expensive overhaul.
A significant challenge in many endoscopic procedures is cable management. There may be many cables typically present in the sterile field: camera cable, fiber optic cable, irrigation and suction, etc. Since the optical fiber cable has the largest diameter it typically is the heaviest cable. One of the challenges that face surgeons using rigid endoscopes is constant rotation of the endoscopes to view different orientation angles. When the endoscopes are rotated, the fiber optic cable is forced to rotate around with the endoscope, thus causing interference. These issues become even more important during arthroscopic surgery. Since the optical fiber cable is heavy, it will actually rotate the endoscope, often forcing the surgeon to keep one of their hands on the fiber optic cable to prevent unwanted spinning of the endoscope.
The illumination fiber also occupies space inside an endoscope or other surgical implement. By allocating space to optical fiber illumination, the diameter of optics may be limited to maintain the smallest overall endoscope diameter.
Typical coupling surfaces to a fiber optic cable are circular, mainly because the fiber cable itself is made with circularly bundled fibers. The problem is accounting for the various sizes of fiber bundles (e.g., 3.0 mm, 3.5 mm, 4 mm, 5 mm diameter bundles are common) to which a light conducting or light guiding device, also called a waveguide device, may be coupled in order to optimize coupling efficiency. Light that is not coupled from the fiber into the waveguide is lost light that cannot be used for illumination. In addition, this lost light may have infrared components that contribute to heating of the coupling connectors, which are typically metal in fiber optic cables. This heating may be significant enough to cause minor to major burns.